Posted by stefanie on Sunday, May 2, 2010 at 11:43am.
2. The new Twinkle bulb has a standard deviation hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be 492 hours.
a. Find the margin of error E for a 90% confidence interval.
Round your answer to the nearest hundredths.

statistics  MathGuru, Sunday, May 2, 2010 at 6:15pm
Margin of error = zvalue (sd/√n)
Find the zvalue corresponding to 90% confidence using a ztable.
sd = standard deviation
n = sample size
I hope this will help get you started.

statistics  Anonymous, Tuesday, June 1, 2010 at 11:54am
Please someone help me? The new twinkle bulb has a standard deviation 35 hours. A random sample of 50 light bulbs is selected from inventory. The sample mean was found to be x=500 hrs. Find the margin of error for 95%, construct a 95% confidence interval for the mean life of all Twinkle bulbs. I am desperate.
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